[Soc-2014-dev] Weekly Report #10: NURBS Modernization

Jonathan deWerd jjoonathan at gmail.com
Sat Jul 26 21:17:26 CEST 2014 

>  [Sergey Sharybin] Last commit was done on Monday

Whoops, I've pushed now. Sorry about that. I have commits showing progress on Mon, Tue, Wed. Thu I spent reading math not writing code and Fri I spent working on the curve tessellation. I will continue to work on it today (Sat), and I'll push what I have at the end of today regardless of whether or not it's complete.

> [Sergey Sharybin]   Before you go to importing or making improvements to curve->mesh, i'll demand wrapping existing code up, making so it's used in blender

All of the code that I have written *is* used in blender. If you mean that I should focus on making trim curves work before fixing convert-to-mesh, then I understand and agree completely. I'm working on trim curves right now.

>  [Sergey Sharybin] Plans for next week?

* If tessellation curves still aren't done, finish them.
* Implement rotation surfaces inside blender
* Get trimming working with rotation surfaces (potentially nasty edge case at singularities and topological wrapping points)

This should bring me to the point of being able to import Claas's hairdryer. That's the demo I am currently aiming to get working.

-Jon


On Jul 26, 2014, at 7:39 AM, Sergey Sharybin <sergey.vfx at gmail.com> wrote:

> Hi,
> 
> It's cool to hear you're doing progress, but what about committing the stuff to Git? Last commit was done on Monday and in the report you claim having progress since that. Commit the stuff even if it's not production ready. I've asked about this several times already.
> 
> Before you go to importing or making improvements to curve->mesh conversion i'll demand wrapping existing code up, making so it's used in blende (and commit everything!)r and preparing demo files for this.
> 
> As for ngon examples, you just need to fill in mpoly and mloop arrays actually. MOD_boolean_util.c has examples (it operates with DerivedMesh, but it's almost the same as you need for curve->mesh conversion).
> 
> Also, what are the plans for the next week?
> 
> 
> On Sat, Jul 26, 2014 at 1:43 PM, Jonathan deWerd <jjoonathan at gmail.com> wrote:
> This week was largely eaten up by a task that I thought would be a quick copy/paste job but turned into a morass of debugging math code. Fortunately that part is done -- and the result is much prettier smooth curves:
> 
> http://wiki.blender.org/index.php/User:Jjoonathan/New_NURBS_Eval
> 
> Progress This Week:
> * Finished the new evaluation code. Key features:
> 	* Computes any number of partial derivatives analytically
> 	* Immediate application 1: compute normals analytically = it looks smooth again :)
> 		* No nasty lighting artifacts near trim edges
> 		* No seams where curves touch/loop due to calculating normals at polygon corners
> 	* Immediate application 2: handle (literal) edge cases of eval points lying on knots correctly
> 	* Immediate application 3: uses 1/2 as many divisions, so possibly it's faster, although I didn't check
> 	* Future application: computing error bounds
> * Performed extensive verification of the new eval code
> 	* Mesh points coincide with Rhino surfaces
> 	* All 1st, 2nd (partial) derivatives agree with Mathematica's NURBS implementation (direction, amplitude correct).
> * Made progress on the trim curve tessellator.
> 	* NOTE: last week I mistakingly said that I had finished the trim curve tessellator when I actually meant to say that I had finished the surface tessellator.
> 	* Refactored the import code so that it can make detatched curves
> 	* Adjusted memory management & blenloader
> 	* The trim curve tessellator isn't a sticking point, I only got around to working on it again today. The eval code was the sticking point.
> 
> Things that were done that don't officially constitute progress:
> * Spent Thursday finishing rotation surface & interpolation surface chapters in P&T
> 
> Things that must be done before I can import the sample .3dm files:
> * Finish the trim curve tessellator
> * Rotation surfaces
> 
> Things I could use help on:
> * Does anyone know of good example code for making a BMesh out of n-gons? N-gons would make the meshes produced by Alt+C *much* cleaner.
> 
> 
> 
> On Jul 19, 2014, at 1:28 PM, claas kuhnen <info at ckbrd.de> wrote:
>> So agree I am very excited about this
>> 
>> On Jul 19, 2014 1:27 PM, "Sergey Sharybin" <sergey.vfx at gmail.com> wrote:
>> Seems to be rather nice progress. Would be cool if all the bits are committed and some .blend in shared which demonstrates the stuff.
>> 
>> 
>> On Sat, Jul 19, 2014 at 4:31 PM, Jonathan deWerd <jjoonathan at gmail.com> wrote:
>> Progress:
>> * Finished code to tessellate trim curves!
>>         see: http://wiki.blender.org/index.php/User:Jjoonathan/NURBS_In_Blender
>> * Rewrote knot code to match the conventions in the math literature, tested for compatibility by comparing meshes
>> * Worked on adapting a better NURBS evaluation algorithm that can produce first and second derivatives (for normals and error bounds, respectively).
>>         it's still buggy.
>> * Worked further on the NurbEdge interface to handle imported trim curves
>>         still working on code to match endpoints that are separated in UV space but coincide in R3 due to either wrapping in UV space (cyclic NURBS) or coving
>> 
>> Todo:
>> * Finish tracking down the NaN-producing bugs in the new surface evaluator
>>         From there, should be easy to implement good normals
>> * Finish NurbEdge so that it at least handles wrapping in UV space. This will allow importing of most .3dm files.
>> * Implement revolution surfaces.
>>         Demo Claas's hairdryer model!
>> 
>> On Jul 12, 2014, at 11:14 AM, Jonathan deWerd <jjoonathan at gmail.com> wrote:
>> 
>> > (Apologies if this is a duplicate email. I see a copy of this email in gmail's "sent" folder but I don't see one in my inbox, so I'm sending again.)
>> >
>> > Progress:
>> > * Finished the code that traverses BReps from 3dm files and cuts them into surfaces
>> > * 2D Trim curves import as Nurb objects that are appended to a NurbList in their parent surface
>> >       Just curves currently, I still have to get multi-part loops working
>> >       Also they don't seem to be preserved by DNA even after calling makesdna...
>> > * Moved surf_gridmesh into bf_blenkernel, promoted curve.c to curve.cpp (for future OpenNurbs use), fixed a few small bugs that caused, moved the GLUT debug code into blender/tests, convinced CMake to build and link it
>> > * Wrote, debugged the method that builds the displist from the gridmesh
>> > * Timed it, see pretty graph a few emails back
>> > * Started writing NurbEdge structure to handle in general the sewing of trim edges and cyclic edges (e.g. so that spheres don't have seams)
>> >
>> > Next up:
>> > * I still need to finish the code that tessellates the trim curves. I didn't get much time to work on it today, so I'm planning to work on it tomorrow as well.
>> > * Get trim curves to load/save from .blend files by figuring out what I'm doing wrong with makesdna
>> > * Finish NurbEdge interface for defining edges to sew, get it in DNA as well
>> > * Use NurbEdge to implement revolution surfaces
>> >
>> 
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>> 
>> 
>> -- 
>> With best regards, Sergey Sharybin
>> 
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> 
> -- 
> With best regards, Sergey Sharybin
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